com.google.firebase.database.DatabaseException：无法将 java.lang.String 类型的对象转换为 com.example.gatewayrestaurant.model1

Question

在片段中显示来自 Firebase 的数据 遇到此错误 我不知道错误是什么 任何帮助将不胜感激 制作一个简单的应用程序，其中 Firebase 数据显示在应用程序中。 ** 我在正常活动中尝试过。 但在片段中，它不起作用**

Model1 类

package com.example.gatewayrestaurant;

public class model1 {

    String image,name,price;

    public model1() {
    }

    public model1(String image, String name, String price) {
        this.image = image;
        this.name = name;
        this.price = price;
    }

    public String getImage() {
        return image;
    }

    public void setImage(String image) {
        this.image = image;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPrice() {
        return price;
    }

    public void setPrice(String price) {
        this.price = price;
    }
}

Myadapter

package com.example.gatewayrestaurant;

public class myadaptersoutindian extends FirebaseRecyclerAdapter<model1,myadaptersoutindian.myviewholder> {


    public myadaptersoutindian(@NonNull FirebaseRecyclerOptions<model1> options) {
        super(options);
    }

    @Override
    protected void onBindViewHolder(@NonNull myviewholder holder, int position, @NonNull model1 model) {
        Glide.with(holder.img.getContext()).load(model.getImage()).into(holder.img);
        holder.menuTitle.setText(model.getName());
        holder.price.setText(model.getPrice());

    }

    @NonNull
    @Override
    public myviewholder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.southindiancardview,parent,false);
        return new myviewholder(view);

    }

    public class myviewholder extends RecyclerView.ViewHolder
    {
        ImageView img;
        TextView menuTitle,price;

        public myviewholder(@NonNull View itemView) {
            super(itemView);

            img=itemView.findViewById(R.id.menu_image);
            menuTitle=itemView.findViewById(R.id.menu_title);
            price=itemView.findViewById(R.id.price);
        }
    }
}

片段

public class ftab1 extends Fragment {

    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    private String mParam1;
    private String mParam2;
    RecyclerView recview;
    myadaptersoutindian adapter;

    public ftab1() {
    }


    public static ftab1 newInstance(String param1, String param2) {
        ftab1 fragment = new ftab1();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.fragment_ftab1, container, false);

        recview=(RecyclerView)view.findViewById(R.id.recview);
        recview.setLayoutManager(new LinearLayoutManager(getContext()));
        FirebaseRecyclerOptions<model1> options =
                new FirebaseRecyclerOptions.Builder<model1>()
                        .setQuery(FirebaseDatabase.getInstance().getReference().child("southindian"), model1.class)
                        .build();

        adapter=new myadaptersoutindian(options);
        recview.setAdapter(adapter);


        return view;
    }
    @Override
    public void onStart() {
        super.onStart();
        adapter.startListening();
    }

    @Override
    public void onStop() {
        super.onStop();
        adapter.stopListening();
    }
}

错误

com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.example.gatewayrestaurant.model1
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertBean(CustomClassMapper.java:436)
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToClass(CustomClassMapper.java:232)
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertToCustomClass(CustomClassMapper.java:80)
        at com.google.firebase.database.DataSnapshot.getValue(DataSnapshot.java:203)
        at com.firebase.ui.database.ClassSnapshotParser.parseSnapshot(ClassSnapshotParser.java:29)
        at com.firebase.ui.database.ClassSnapshotParser.parseSnapshot(ClassSnapshotParser.java:15)
        at com.firebase.ui.common.BaseCachingSnapshotParser.parseSnapshot(BaseCachingSnapshotParser.java:36)
        at com.firebase.ui.common.BaseObservableSnapshotArray.get(BaseObservableSnapshotArray.java:52)
        at com.firebase.ui.database.FirebaseRecyclerAdapter.getItem(FirebaseRecyclerAdapter.java:109)
        at com.firebase.ui.database.FirebaseRecyclerAdapter.onBindViewHolder(FirebaseRecyclerAdapter.java:149)
        at androidx.recyclerview.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:7065)
        at androidx.recyclerview.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:7107)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:6012)
        at androidx.recyclerview.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6279)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6118)
        at androidx.recyclerview.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:6114)
        at androidx.recyclerview.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2303)
        at androidx.recyclerview.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1627)
        at androidx.recyclerview.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1587)
        at androidx.recyclerview.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:665)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:4134)
        at androidx.recyclerview.widget.RecyclerView.dispatchLayout(RecyclerView.java:3851)
        at androidx.recyclerview.widget.RecyclerView.onLayout(RecyclerView.java:4404)
        at android.view.View.layout(View.java:23750)
        at android.view.ViewGroup.layout(ViewGroup.java:7277)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at android.view.View.layout(View.java:23750)
        at android.view.ViewGroup.layout(ViewGroup.java:7277)
        at androidx.viewpager.widget.ViewPager.onLayout(ViewPager.java:1775)
        at android.view.View.layout(View.java:23750)
        at android.view.ViewGroup.layout(ViewGroup.java:7277)
        at androidx.constraintlayout.widget.ConstraintLayout.onLayout(ConstraintLayout.java:1855)
        at android.view.View.layout(View.java:23750)
        at android.view.ViewGroup.layout(ViewGroup.java:7277)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at android.view.View.layout(View.java:23750)
        at android.view.ViewGroup.layout(ViewGroup.java:7277)
        at androidx.appcompat.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:530)
        at android.view.View.layout(View.java:23750)
        at android.view.ViewGroup.layout(ViewGroup.java:7277)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at android.view.View.layout(View.java:23750)
        at android.view.ViewGroup.layout(ViewGroup.java:7277)
        at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1829)
        at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1673)
2021-01-28 10:42:28.545 3914-3914/com.example.gatewayrestaurant E/AndroidRuntime:     at android.widget.LinearLayout.onLayout(LinearLayout.java:1582)
        at android.view.View.layout(View.java:23750)
        at android.view.ViewGroup.layout(ViewGroup.java:7277)
        at android.widget.FrameLayout.layoutChildren(FrameLayout.java:332)
        at android.widget.FrameLayout.onLayout(FrameLayout.java:270)
        at com.android.internal.policy.DecorView.onLayout(DecorView.java:1099)
        at android.view.View.layout(View.java:23750)
        at android.view.ViewGroup.layout(ViewGroup.java:7277)
        at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:3712)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:3164)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:2225)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:9126)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:999)
        at android.view.Choreographer.doCallbacks(Choreographer.java:797)
        at android.view.Choreographer.doFrame(Choreographer.java:732)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:984)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:237)
        at android.app.ActivityThread.main(ActivityThread.java:8167)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)

在片段中显示 Firebase 数据的任何其他方法也可以使用。

Answer 1

您收到以下错误：

<块引用>

com.google.firebase.database.DatabaseException：无法将 java.lang.String 类型的对象转换为 com.example.gatewayrestaurant.model1 类型

因为您正在传递以下引用：

FirebaseDatabase.getInstance().getReference().child("southindian")

对于“setQuery()”方法，这意味着该引用下的每个子项都将呈现为“model1”类型的对象。这实际上是不可能的，因为在“southindian”节点下，只有三个 String 对象存在，因此出现错误。请记住，在 Java 中，您无法转换 String tp "model1" 类型的对象，因为它们之间没有继承关系。

我个人怀疑，但如果“menu”子项与“southindian”子项具有相同的属性，那么您应该传递给该方法，参考如下：

FirebaseDatabase.getInstance().getReference()

没有调用 .child("southindian")。这意味着每个孩子都将被视为“model1”类型的对象。如果不是这种情况，则删除第一个“菜单”子项或尝试在单个节点中创建另一个模式，以仅存储相同类型的对象。